"Simon Peyton-Jones" <simonpj@microsoft.com> writes:

So I'm interested to know: if GHC allowed arbitrarily-ranked types, who would use them?

I can't promise that I would use them, but it would certainly give me warm fuzzy feelings to know that they were there. :-) On the other hand, I believe that you can construct in GHC a type which is isomorphic to any arbitrarily-ranked type (with any combination of existential and universal quantification) by creating new data constructors. If this is true, then I'm reasonably content with that. Carl Witty